1. Field of the Invention
The present invention relates to an apparatus and method for automatically searching for feature points of an object, and more particularly, to an apparatus and method for accurately searching for feature points of an object in an image in which the pose of the object changes greatly.
2. Description of the Related Art
An active shape model (ASM) is an analytical model capable of extracting the shape of an object included in a new image, by using a statistical shape model after generating the statistical shape model of the object to search for by using training sets given in advance. Here, each training set consists of face images on which feature points of an object to search for are labeled, and the shape in each training set is a set of n labeled landmarks, that is, n feature points. In the ASM, correlation with which feature points labeled differently to each other move is modeled, as the shape of an object changes. Each of labeled feature points can be made to be one vector, and by performing a principal component analysis for all vectors generated in relation to the training sets, the shape can be described using an appropriate number of coefficients. According to the ASM, a statistical shape model can be iteratively changed to match an object in a new image. The shape change in the statistical shape model of ASM is restricted, so that the shape change is made only in the direction shown in labeled training sets.
However, in the ASM which is currently used for searching for feature points of a face image, the positions of feature points of an average face image obtained from training sets formed with a plurality of front face images are used. Accordingly, when the pose of the face in the input image changes greatly, it is difficult to correctly search for feature points, for example, because the positions of feature points are diffused. In addition, since an ASM profile formed with 1-dimensional templates is used in order to determine the positions to which feature points will move in a face image, there is a possibility that the ASM falls into a local minimum, in particular pose variation.
An article related to and generally discussing ASM was written by T. F. Cootes, C. J. Taylor, D. H. Cooper, and J. Graham entitled “Active Shape Models-Their Training and Application”, Department of Medical Biophysics, University of Manchester, Oxford Road, Manchester M13 9PT. England, Computer Vision and Image Understanding Vol. 61, No. 1, pp. 38-59, January 1995.